Could it be his epson salts on his roots? I had some bakeing soda on some of my roots once close to the netpot. I know for sure cause it foamed when I dunked my finger in vinegar. Wasnt grainy though and it was from a plant that was just a bubble bucket, no rez and it was accompanied with some white foam I associated with my water being to warm. Wasnt that much though
....LMAO!!... I've since taken to adding a little alcohol into the fluid res',... *** AH! I see you posted up in the higher traffic LHT... there are a few other folks here who might know what this glop is!